The present invention provides visual inspection and physical access into the space of a fluid containment system consisting of an inner storage container or vessel, and an outer, reinforced precast structure, or vault, having a top cover. A CPU connected to a memory module is positioned in the handset, the memory module having a plurality of message storage locations corresponding to the keys of the keypad. For this reason, it is feasible to securely prevent an electroconductive member 14 in the through hole 13 from dissolving into a molten solder 25, during connection of a lead wire 24 to an outside layer 23 of the terminal electrode 17 by the solder 25, and to securely prevent breakage of electrical connection in the through hole 13.